A while ago, Ollie had a big sore on the back of his neck which I thought was a reaction to Frontline. One vet said it was a food allergy and gave Ollie a steroid injection to stop the itching and I had to apply cortisone cream to the spot . I wasn't happy with the treatment and took him to another vet who discounted the allergy and was doubtfull about the Frontline too. She continued with the injections every 10 days for a month plus, the cream. Frankly we never did find the cause and it took a good 3 months or more before it really healed, Ollie could scratch, but not lick, the spot. Eventually when it seemed to be under control, she told me to apply Cothivet which comes in a spray bottle and contains essense of lavender, rosemary and other lovely smelly things. This was to help the wound to dry up and heal, which it eventually did and the fur grew back. I have applied Frontline since then with no problems so I may never know what it was.